Such a lighting system is, e.g., known from U.S. Pat. No. 3,860,811, wherein a flashlight emitting beams of different widths is disclosed. The flashlight comprises a light source and a lens for refracting the light coming from the light source. A lens chamber is situated in between the light source and the lens and is in fluid communication with a storage chamber. When the flashlight is in a first orientation, the lens chamber is filled with liquid, and light from the light source passes both the liquid and the lens before leaving the flashlight. When the flashlight is rotated to a second orientation, gravity pulls the liquid out of the lens chamber into a storage chamber outside the light path. The light from the light source then only has to pass the empty lens chamber and the lens before leaving the flashlight. The width and the intensity of the light beam thus depend on the orientation of the flashlight.
One disadvantage of the flashlight of U.S. Pat. No. 3,860,811 is that the lens chamber and the storage chamber must be manufactured and filled with liquid such that they are perfectly sealed in order to prevent the fluid from leaking out. Even a small leak may reduce the quality of the produced light due to evaporation of the liquid. In addition, contamination or small protrusions at the lens chamber surface may cause drops of liquid to stay behind in the lens chamber when all liquid should go to the storage chamber, which leads to undesirable disturbances of the emitted light beam.
Another possible way to obtain gravity-controlled light effects is disclosed in, e.g., the international patent application published under number WO 03/008858 A1, disclosing a lighting system using three tilt switches for detecting an orientation of the system. The tilt switches are coupled to a programmable logic circuit. The programmable logic circuit is coupled to light emitting means arranged for producing various lighting effects, depending upon the detected orientation of the lighting system.
It is a disadvantage of this lighting system that the complex electronics have a risk of malfunctioning. Furthermore, many lighting effects require displacement of optical elements. For electronic control of such displacement, additional complex and bulky actuator components are needed.